EFFECTS OF THE CORTICOTROPIN-RELEASING FACTOR (CRF) ON RECTAL AFFERENT NERVES IN HUMANS

Corticotropin-releasing-factor (CRF) released in the gastrointestinal mucosa from immune cells or enterochromaffin cells may play a role in the modulation of rectal afferent function. In the current study we ev aluated the effects of peripherally administered CRP on afferent mecha nisms in the human rectum. We used rectal balloon distention in seven healthy volunteers to evaluate the effect of CRF (1 mu g/ kg) on visce ral afferents originating in the rectum which are involved in the foll owing functions: thresholds and intensity of conscious perception, rec eptive relaxation, reflex inhibition of internal anal sphincter and a viscerosomatic reflex. Rectal mechanoreceptors were stimulated either by distending the rectum using a volume ramp (40 and 400 mL/min), or b y intermittent phasic distention. CRF decreased the thresholds and inc reased the intensity for the sensation of discomfort in response to bo th ramp and phasic distention. During slow ramp distention, CRF also l owered the stool threshold. CRF increased rectal compliance during slo w ramp distention without affecting the rare of receptive relaxation o r the inflection point of the compliance curve. CRF had no effect on v iscerosomatic referral patterns, or on the rectoanal inhibitory reflex . These findings are consistent with a dual effect of CRF on afferent pathways mediating perception of aversive rectal sensations, and on re ctal smooth muscle.